I like my freeflow Tf5, just like anything, once you learn how it works and how to maintain, its a killer gun.
F5's use sensor technology for timing on a shot per shot basis. Once the sensors are in the right place, cocking block, and sear catch is adjusted, its all auto from there.
Racegun you need to set timing manually, and it seems each one requires different settings. Please know I have never used a Racegun, and I"m sure they are awsome too. I'm just comparing technologies.
F5 Tiny Tornado
Defiant w/chaos chip - now backup :)
IC Panther (one of first 200 made!)
Sterling - pumps still rock